NEW YORK (Bloomberg) — Steve Miller, who was promoted to chairman of American International Group Inc. three months ago, will be interim chief executive officer of the bailed-out insurer if Robert Benmosche steps down while fighting cancer.

Miller will take the post "in the event that Bob would become unwilling or unable to continue to effectively serve in his current role", the New York-based insurer said yesterday in a statement. Miller, 68, would have the job "for as long as it takes to identify and select a long-term replacement".

Benmosche, 66, told staff this week that he had begun an "aggressive round of chemotherapy" and that the company was preparing for alternatives if he had to limit his work. AIG announced a plan last month to regain independence and repay its $182.3 billion US rescue that hinges on selling stock to private investors as early as the first quarter.

"They're telling the world things will be under control no matter what happens to their leadership," said Jeanne Branthover, a managing director at Boyden Global Executive Search Ltd. in New York. AIG made a "credible choice that will be viewed positively internally and externally".

Miller replaced Harvey Golub as chairman of AIG in July 2010, after Benmosche threatened to leave the company unless Golub resigned. Miller oversaw the bankruptcy of auto-parts supplier Delphi Corp. and helped Chrysler Corp. return to profitability after taking government loans in 1980. He has been CEO at Waste Management Inc. and Bethlehem Steel Corp.

He wrote an autobiography called "The Turnaround Kid: What I Learned Rescuing America's Most Troubled Companies", in April 2008. In the book, Miller looked back over a career that started at Ford Motor Co. in 1968.

Under Benmosche, AIG is focusing on global property- casualty coverage and US life insurance and retirement services after striking deals to sell non-US life insurers and consumer-finance operations to help repay the US.

AIG surged 39 percent this year through yesterday in New York trading after slipping 4.5 percent in 2009 and plunging 97 percent in 2008, the year housing-market related losses pushed the firm to the brink of collapse.